Answer:
108 one-bedroom units
72 two-bedroom units
36 three-bedroom units
Step-by-step explanation:
Let x, y, z the number of one-bedroom, two-bedroom and three-bedroom units respectively. Then
1) x+y+z = 216
2) y+z = x
3) x = 3z
Multiplying equation 1) by -1 and adding it to 2), we get
-x = x-216 so, x = 216/2 = 108
x = 108
Replacing this value in 3) we get
z = 108/3 = 36
z = 36
Replacing now in 2)
y+36 = 108, y = 108-36 and
y = 72